Consistency between
laboratory tests is important and yet the results may depend on who
did the test and where the test was performed. In an experiment to
test levels of consistency, a large jar of dried egg powder was
divided up into a number of samples. Because the powder was
homogenized, the fat content of the samples is the same, but this fact
is withheld from the laboratories. Four samples were sent to each of
six laboratories. Two of the samples were labeled as G and two as H,
although in fact they were identical. The laboratories were
instructed to give two samples to two different technicians. The
technicians were then instructed to divide their samples into two
parts and measure the fat content of each. So each laboratory
reported eight measures, each technician four measures, that is, two replicated
measures on each of two samples.